Lennon's men went into the game on the back of five successive defeats, but late goals from Conor Newton and Gregg Wylde secured a vital win as the Buddies attempt to climb away from the relegation play-off place.
Lennon said: "There was a lot of talk at training this week from myself and my staff and the players.
"Everyone wore their heart on their sleeves and I was absolutely delighted to see they carried that out there today.
"They were certainly committed and passionate. The way they hunted the ball in all areas of the pitch, they certainly got their rewards."
And Lennon praised substitute Wylde for his contribution after the winger set-up the first goal before sealing the points with an excellent finish.
"I have to compliment him. For not being in the starting line-up, he gives you the reaction that every manager wants out there," .Lennon added.
"It's been a long time since we have had that quality on the pitch and that quality to replace it with."
Kilmarnock counterpart Allan Johnston conceded his side had been poor in the first half, but felt they might have got something when substitute Robbie Muirhead provided a spark after replacing Alexei Eremenko at the break.
"The first half was very even and really scrappy but it broke up in the second half and both teams had opportunities," Johnston said. "Obviously theirs went in.
"The first half we never showed the energy or passed the ball well enough. The second half, with the introduction of big Robbie, we looked a better team and looked a lot more threatening going forward."